Blast-valve operation for gas-blast circuit breakers having two currentresponsive means



UCL 3, 1967 R. G. coLcLAsER, JR., ETAL 3,345,486

BLAST-VALVE OPERATION FOR GAS-BLAST CIRCUIT BREAKERS HAVING TWO CURRENT-RESPONSIVE MEANS Filed Oct. 29, 1964 5 SheebS-Sheet l Robert G. Colclaser, Jr. and Charles E Cromer ZLZZM@ @fr ATTORNEY 0d 3. 1967 R. G. COLCLASER, ETAL 3,345,486

BLAST-VALVE OPERATION FOR GAS-B ST CIRCUIT BREAKERS HAVING TWO CURRENT-RESPONSIVE MEANS 5 Sheets-Sheet 2 Filed Oct. 29, 1964 Oct. 3 1967 R. G. COLCLASER, JR., ETAL 3,345,486

BLAST-VALVE CPERATION FOR GAS-BLAST CIRCUIT BREAKERS HAVING TWO CURRENT-RESPONSIVE MEANS 3 Shets-Sheet 5 Filed Oct. 29, 1964 HIGH 54 PRESSURE HUGH v PRESSURE United States Patent O 3,345,486 BLAST-VALVE OPERATIGN FOR GAS-BLAST CIR.

CUIT BREAKERS HAVING TWO CURRENT- RESPONSIVE MEANS Robert G. Colclaser, Jr., Franklin Township, Belmont, and Charles F. Cromer, Penn Township, Trafford, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 29, 1964, Ser. No. 407,294 Claims. (Cl. 2011-148) This invention relates, generally, to circuit breakers and, more particularly, to the operation of blast valves for gas-blast type circuit breakers having two current responsive means.

Oil circuit breakers have proven somewhat insensitive to both current and recovery voltage rate. Generally, their method of interruption is based on the self-generated principle, resulting in higher pressures at higher currents and, hence, increased interrupting eifort. Gas breakers of the double-pressure type, in which gas is stored .at high pressure and blasted through an orice type interrupter to a low-pressure region by opening a blast valve, have maximum interrupting effort at low values of current. This latent interrupting effort can interrupt increasing values of current until a given current is reached. At this, and all higher currents, failure results. Because of clogging effects, the severity of the recovery voltage is also a factor. Current .and recovery, voltage combine t-o place a limit on the interrupting ability of a dual-pressure gasblast breaker.

An object of this invention is to provide a blast valve for a gas-blast circuit breaker which is opened at load and low fault currents by mechanical means and at higher fault currents by electromagnetic means.

A further object of the invention is to provide means for utilizing most of the .available reservoir pressure during an interruption.

Another object of the invention is to provide a failsafe means for operating the blast valve of a gas-blast type off circuit breaker.

Another object of the invention is to provide an improved compressed-gas circuit interrupter in which an inductive device, responsive to the magnitude of fault current ilow through the circuit interrupter, is utilized to `immediately effect blast-valve operation upon initiation .of a heavy fault condition. l A further object is to provide an improved compressedgas circuit interrupter in which .a current transformer is utilized, in conjunction with mechanical means, for effecting the opening of the `associated blast valve.

Other objects of the invention will be explained fully hereinafter, or wi-ll be apparent to those skilled in thel art.

In accordance with one embodiment of the invention, the blast Valve of a dual-pressure gas-blast type circuit breaker is opened mechanically by `a linkage system at l, currents below a predetermined value. At higher fault currents, the blast valve is opened by levers actuated by electromagnetic devices energized by the current in a sec- ,ondary winding on an iron core surrounding one of the terminal conductors carrying the breaker current. The

core has an air gap therein t-o prevent saturation evenl when relatively high fault currents are flowing through the terminal conductor of the breaker. Thus, at high shortcircuit fault currents, the blast valve is opened when the heavy current fault is initiated, thereby permitting the effective use of high-pressure gas at a series of interrupters yconnected to a single reservoir. The mechanically-operated feature is retained for load currents and for lowcurrent fault interruption, land as a fail-safe yfeature at vhigh fault currents.

For a better understanding ofthe nature and objects u 3,345,486 Patented Oct. 3, 1967 partly in section, and partly in top plan, of the structure shown in FIG. 3; and,

FIGS. 5 and 6 are graphical views illustrating operational features of the invention.

Referring to the drawings, .and more particularly to FIG. 1 thereof, a current conductor 11 is disposed at the center of an iron core 12 of a current-transformer device CT. The core 12 has an air gap 13 therein. A secondary coil 14 is wound on the core 12. The secondary coil 14 is connected in series-circuit relation with au actuating coil 15 of an electromagnetic device 9 having an armature 16, which is actuated when a predetermined current flows through the coil 15. The armature 16 is connected to a pivoted lever 17, which opens a blast valve 18, that normally closes the outlet from a high-pressure reservoir 19. Assuming that the conductor 11 is one of the terminal conductors for a circuit-breaker pole-unit, this conductor 11 will carry the short circuit, or fault current, flowing through the pole-unit of the breaker. The air gap 13 prevents saturation of the iron core 12, even when relatively high fault currents, such as 45,000 to 55,000 amperes, for example, ilow through it. The ux produced in the core 12 by the heavy fault current in the conductor 11 induces a current in the secondary coil 14, which flows through the solenoid coil 15, thereby actuating the armature 16 and rotating the lever 17 to open the blast valve 18. It will be understood that the current transformer CT and the electromagnetic device 9 may be so constructed that the valve 18 is opened by the device only when a `relatively high-value fault current is owing through the conductor 11, which functions as the primary winding for the current transformer CT.

Referring to FIG.V 2, a circuit breaker 21 shown therein may be of the type described in a copending application Ser. No. 61,284, led Oct. 7, 1960, now U.S. Patent 3,154,658, issued Oct. 27, 1964, to R. G. Colclaser and R. N. Yeckley, and assigned to the Westinghouse Electric Corporation. The breaker 21 is a three-pole breaker suitable for controlling the three-phases A, B and C of a transmission system. As shown, the circuit breaker 21 comprises a plurality of generally horizontallyextending grounded metallic tanks 22 having end covers 23 attached thereto. The end covers 23 may be opened or removed to permit inspection of the interior of each tank 22, and withdrawal of an arc-extinguishing assembly 24 (FIG. 3), which is disposed inside each tank 22. A portion of one arc-extinguishing assembly 24 is shown in FIG. 3.

Upwardly extending cylinders, or collars 2S, are disposed near opposite ends of each tank structure 22. Each collar 25 has a hanged, apertured upper support plate 26, which supports a terminal bushing 27. As well known in the ait, the terminal bushings 27 serve the function of carrying the. current to be interrupted into the interior of the tank structures 22. In addition, Va's more clearly shown in FIG. 3, the lower ends 28 of the terminal bushings 27 serve to support the arc-extinguishing assemblages 24 inside the tanks 22.

An auxiliary high-pressure storage tank 31 is disposed below each low-pressure tank 22. Each tank 31 is connected to one of the high-pressure reservoirs 19, which is located inside 4each low-pressure tank' 22 -at one-end o of the assemblage 24. The storage tanks 31 and the reservoirs 19 contain an interrupting fluid, such as, for example, sulfur-hexafluoride (SFS) gas, at a relatively high pressure, although other arc-extinguishing gases, such as air, may be used. A mechanism housing 32 is provided, which encloses gas-control equipment and a suitable compressor (not shown), which is utilized to withdraw relatively low-pressure gas from the interior of the tanks 22, to recompress it and to return it to the high-pressure storage tanks 31 and 19.

A suitable operating mechanism is also disposed within the housing 32. The mechanism may be of the pneumatic type which functions, by suitable linkage, to effect reciprocal motion of an operating shaft disposed interiorly of a tube 35, which interconnects the lseveral pole-units A, B and C.

A current transformer, or rst current-responsive means 36 encircles each of the terminal bushings 2'7.

The current transformers 36 may be utilized to measure the current ow through the circuit breaker 21 and also to operate the protective relaying equipment. Conduits 37 carry the secondary leads of the current transformers 36 into the housing 32, in which a suitable trip mechanism mayv be located. The entire breaker structure 21 may be mounted on suitable supporting beams 34.

As previously explained, the arc-extinguishing assembly 24 is, in general, similar to the one described in the aforesaid U.S. Patent 3,154,658. The assembly 24 may be of the multi-break type, having two or more interrupter units 38 connected in series circuit relation. Each end of the assembly 24 is supported by a support casting 39, which, in turn, is supported by the lower end 28 of the respective terminal bushing 27. The highpressure reservoir 19 is attached to the `support casting 39; and the blast valve 18 controls the admission of the high-pressure interrupting fluid from the reservoir 19 into a region 41 inside the support casting 39.

The interrupting unit 38 comprises an interrupting chamber 42, which is attached to the support casting 39 by means of a clamping ring 43. The interrupting chamber 42 is preferably composed of polytetrafluoroethylene, which is sold under the trade name Teon. A generally tubular movable contact member 44 is engaged by a cluster of stationary contact fingers 45 inside the interrupting chamber 42. The base of the cluster of stationary contactngers 45 is attached to the support casting 39 by means of an arc horn 46. When the contact members 44 and 45 are separated in the manner described in the aforesaid copending patent application, an arc (not shown) is drawn between the movable contact 44 and the stationary lingers 45, which transfers to the arc horn 46 and is then extinguished by a blast of interrupting iuid, which is admitted into the entrance region 4,1 by the opening of the blast valve 18, and flows into the interrupting chamber 42, as inldicated by the arrows 47. The interrupting uid also flows to the other interrupters 38 through insulating blast tubes 48, as indicated by the arrow 49. The blast valve 18 is opened in conjunction with the separation of the contact members 44, `45 of the interrupting unit 38 by a mechanical means, shown generally by the reference numeral 51. The valve-operating mechanism 51 may be of the type described in a copending application Ser. No. 63,201, tiled Oct. 17, 1960, now U.S. Patent 3,164,704, issued Ian. 5, 1965, to R. N. Yeckley, Joseph Sucha and R. C. Van Sickle, and assigned to the Westinghouse Electric Corporation. As described in the aforesaid U.S. Patent 3,164,704, the right-hand ends of two laterally-spaced longitudinally-movable operating rods (not shown), which constitute a part of the movable contact assembly 40, are pivotally connected .to links 52. The links 52 have their right-hand ends separately connected, by pivot pins 53, to spaced bifurcated arms 54 of a main contact operating lever casting 55 pivotally mounted on a stationary pivot shaft 56.

An operating pull rod 57 (FIG. 2), which is connectedv by crank means to the operating rod within tube 35, is utilized to effect clockwise closing rotative motion of the contact lever casting 55 and consequent compression of an accelerating spring (not shown), which supplies the energy for opening the contact members of the interrupting units 38. The circuit-breaker operating mechanism within compartment 32 is latched by Isuitable means in the closed-circuit position of the circuit breaker 21. During the opening operation of the breaker, the latching means is released by the tripping mechanism, and the accelerating spring drives the moving contact assembly 46 to the left, as shown in FIG. 3, thereby rotating the operating lever 55 counterclockwise about its pivot shaft by means of the two links 52.

As shown in FIG. 3, the blast valve 18 is slidably disposed in a generally cylindrical guide portion 58 constituting a part of the high-pressure reservoir 19. A compression spring 59, disposed inside the valve 18 and the guide portion 58, biases the valve 18 to the closed position against a valve seat 61. The valve 18 has a valve stem 62 having a relatively large striker plate 63 attached thereto. The valve 18 is of the ballanced-pressure type having apertures 64 provided through its face to permit thereby communication between the entrance region 41 on the downstream side of the seat 61, and the region 65 within the enclosed space behind the valve 18.

As shown in FIGS. 3 and 4, the striker plate 63 is engaged by the tip end 66 of a pivotally-mounted blastvalve operating lever 67. The operating lever 67 is pivotally mounted on a stationary pivot shaft 68. Integrally formed with the lever 67 is a laterally-extending ratchet portion 69 having a plurality o-ratchet teeth 7,1 thereon. The teeth 71 are engaged by the nose 72 of a pivotally mounted actuating pawl 73 whenever the contact members 44, 45 of the breaker are closed sufcientlyto establish the main circuit.

The pawl 73 is pivotally mounted, as at 74, to a rotatable arm 75, which pivots around the pivot shaft 68 independently of the lever 67. Connecting links 76, only one of which is shown, are connected to the rotatable arm 75 by pivot pins 77. The other ends of the links 76 are connected to a pivot pin 78 which extends transversely between two spaced arms 79 0n the main lever casting 55.

The right-hand end ofthe pawl 73 has a tail extension 81, which is bifurcated and supports a pin 82. A second transversely extending pin 83 extends between the two lspaced links A'76. A spring housing 84, containing acompression spring 85, is supported by the pins 82 and 83. Thus, the compression spring 85 effects a clockwise biasing action of the pawl 73 about its pivotal support 74.

A cam plate 86 is attached to the support casting 39. The plate 86 has a cam surface 87, which engages the Iiose 72 of the pawl 73 to release the pawl 73 from y'che ratchet teeth 71 at exactly the same blast-valve opening,

regardless of which particular tooth 71 is engaged by the pawl 73. In this manner the blast valve 18 is opened mechanically when the main lever 55 is rotated counterclockwise by the links 52 during the separation of the `contact members 44, 45 of the interruptor units 38.

At currents up to a predetermined amount, for example, 22,000-ampere fault current, the blast valve 18 is opened mechanically by the valve-actuating mechanism 51 in the manner just described. Since the region 65 behind the valve 18 is at low pressure, high-pressure gas from the region 88 inside the reservoir 19 acts on the face of the valve 18 snapping it open. This iills the entrance region 41 with high-pressure gas, which ows into Vthe first interrupter unit 38, and also into the additional interrupter units 38 through the blast tubes 48. The blast valve 18 is reclosed by the spring 59 after the pressure on both sides of the valve 18 s equalized by gas flowing through the apertures 64 and after the lever 67 is released from the pawl 73 by the cam lplate 86.

It will be noted that the blast valve 18 is not opened mechanically until after the starting of the separation of the contact members 44, 4S of the interrupter units 38. This is satisfactory for interrupting relatively low-value currents. In order to interrupt currents higher than a predetermined amount, for example the 22,000-ampere fault current magnitude previously mentioned, the electromagnetic means 9, shown diagrammatically in FIG. 1, and hereinbefore described, is utilized. As shown in FIG. 3, the core 12 of the electromagnetic means 9 is mounted on the reservoir ycasting 19 and surrounds the Alower end 28 of Vthe terminal bushing 27. The air'gap 13 in the core 12 prevents excessive heating when load currents are carried. The pick-up secondary coil 14 is connected to two magnet assemblies 2G by conductors 91. The inductive device 9 constitutes a linear coupler associ-ated with the terminal bushing 27.

As shown most clearly in FIG. 4, the two magnetic assemblies 20 are mounted on opposite sides of the support casting 39. The coils 15 on the two magnets 20 are connected in series by a conductor 92, and, as previously explained, they are connected to the pick-up secondary coil 14 by the conductors 91. The armature 16 of each magnetic assembly is pivotally attached to one end of one of the blast-valve operating levers 17. Each lever 17 is pivotally mounted on the support casting 39 by means of a pin 93. The other end of each lever 17 engages the striker plate 63 affixed to the valve stem 62. Thus, when a fault current above a predetermined amount, for eXample 22,00() amperes, iiows through the circuit breaker 21, the electromagnets 20 are energized by the secondary coil 14 to actuate the levers 17 to thereby open the blast valve 18. Once the valve starts to open, it is snapped fully open by the high gas pressure and in the manner hereinbefore described. The valve 18 is opened when the heavy current fault is initiated. The valve 18 is prevented from reclosing by the levers 17 until after the heavy current fault is interrupted. The levers 17 are returned to their normal position by the closing movement ofthe blast valve 18..

Overtravel stops 96 Iare provided on the support cast- -ing 39. e

Before the contact'members 44, 45 part, the entrance region, generally denoted by 41 in FIG. 3, should-be relatively gas-tight. Accordingly, a loose-fitting plug 97 is mounted on the arc horn 46. This definitely closes the center of the hollow moving contact members 44, 4S are ready to separate.

The advantages of the present method of operation are apparent when the operation of the lpresent breaker as described in U.S. Patent 3,164,704 is considered. Shown in FIG. 5 is the sequence of operation when a fault is initiated on the line controlled by thecircuit breaker 21. Fault currentv starts at time 109, the trip coil is energized yat time 110, contact motion begins at time 111, the blast valve 18 is opened mechanically at time 112, the contacts part at time 113, and the current is interrupted at time 114. Assuming a three-break interrupter 24, gas pressure starts to rise in the three interrupting units 38 at points 115, 113 and 116, respectively.

A typical pressure-time curve is shown in FIG. 6. It will be noted that only a fraction of the available reservoir pressure is used for interruption. By increasing the reservoir pressure, a new curve 120 results in a slight increase in interrupting ability. This indicates that if a point 117 on the curve could be reached at the time 114, a greatly improved interrupting ability could be obtained. The principle illustrated in FIG. 1, hereinbefore described, permits the blast valve 18 to be opened by the time point 110 in FIG. 5 is reached, providing approximately two cycles additional time for the gas pressure in each interrupter unit 38 to build up before the contacts 44, 45 part. The curve 125 in FIG. 5 is the voltage generated by induction in the secondary winding 14 as a result of the 44 until the contact fault current passing through the circuit breaker 21. As shown by the preceding analysis, this results in a greatlyimproved interrupting ability for the circuit breaker. The structure shown in FIGS. 3 and 4, and hereinbefore described, utilizes the principle illustrated in FIG. 1.

The structure has the additional .advantage of being somewhat fail-safe, in that the valve 18 is always opened mechanically at a later time in the event that it is not opened electromagnetically prior to the operation of the mechanical means. The valve 18 is normally opened at low currents and low-value fault currents by the mechanical means 51 and at high valve fault currents by the electromagnetic means 20. The interrupting ability of the breaker 21 consequently increased since the blast valve l18 is opened at high-value fault currents even Abefore the contact members 44, 45 of the interrupter units 38 start to separate.

Since numerous changes may be made in the abovedescribed construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that the subject matter hereinbefore described, and shown in the accompanying drawings shall be interpreted as illustrative, and not in a limiting sense.

We claim as our invention:

1. In a compressed gas-type of circuit breaker, in com- ;bination, first electromagnetic means responsive to the magnitude of the current ow through the breaker, means defining a high-pressure storage Areservoir containing an interrupting gas under pressure, a circuit-interrupter unit, a blast valve for admitting gas under pressure from the reservoir into the interrupter unit for extinguishing purposes, mechanical means responsive to said first electromagnetic means for opening the valve at low currents, and second electromagnetic means responsive to the current vflowing through the circuit breaker for opening the valve only at high currents whereby an increased time of valve opening is obtained during heavy fault current interruption.

2. In a compressed-gas type of circuit breaker, in combination, first electromagnetic means responsive to the magnitude ofthe current fiow through the breaker, means defining ahigh-pressure storage reservoir containing an interrupting `gas under pressure, a circuit-interrupter unit, a blast valve for admitting gas under pressure from the reservoir into Vthe interrupter unit for extinguishing purposes, mechanical means responsive to said first electromagnetic` means for opening the valve at low currents,

electrically-operated means independent of said first .electromagnetic means for also opening the valve only at high magnitude fault currents, a transformer responsive only to high magnitude fault current flowing through the circuit breaker for energizing the electrically-operated means whereby an increased time of valve opening is obtained during heavy fault current interruption, Iand said ytrans-former having an iron core with an air gap therein to prevent saturation.

3. In a compressed-gas type of circuit breaker, in combin'ation, first electromagnetic means 4responsive to the magnitude of the current flow through the breaker, means defining a high-pressure storage reservoir containing an interrupting gas under pressure, an interrupting chamber, contact members separable within the interrupting chamber, a blast valve for admitting gas under pressure from the reservoir into the interrupting chamber for arc extinction, mechanical means responsive to said first electromagnetic means operable in conjunction with the separation of the contact members for opening the blast valve, and electromagnetic means separate from said first electromagnetic means for opening the valve prior to the operation of the mechanical means only under predetermined high-current fault conditions whereby an increased time of valve opening is obtained during heavy fault current interruption.

4. In a circuit breaker, in combination, first electromagnetic means responsive to the magnitude of the current llow through the breaker, a low-pressure tank, a highpres-sure storage reservoir containing an interrupting fluid, an interrupting chamber within the tank, Contact members separable within the chamber, a blast Valve -for admitting fluid from the reservoir into the interrupting chamber, mechanical means lresponsive to said iirst electromagnetic means operable in conjunction with the separation of the contact members for opening the blast valve, electromagnetic means separate from said first electromagnetic means for opening the valve prior to the operation of the mechanical means only under predetermined high fault current conditions, and a transformer responsive to the current owing through the circuit breaker for energizing the electromagnetic means only under predetermined high-current lfault conditions whereby an incerased time of valve opening is obtained during heavy fault current interruption.

5. In a circuit breaker, in combination, first electromagnetic means responsive to the magnitude of the current flow through the breaker, a low-pressure tank, a

high-pressure storage reservoir containing an interrupting fluid, an interrupting chamber within the tank, contact members separable within the interrupting chamber, a blast valve for admitting fluid from the reservoir into the interrupting chamber, mechanical means responsive to said rst electromagnetic means operable in conjunction with the separation ofthe contact members for opening the blast valve, separate electromagnetic means for opening the valve prior to the operation of the mechanical means only under predetermined high fault current conditions, a transformer responsive only to high fault current conditions flowing through the circuit breaker for energizing the separate electromagnetic means whereby an increased time of valve opening is obtained during heavy fault current interruption, and said transformer having an iron core with an air gap between therein to prevent saturation even at relatively high currents.

6. A circuit breaker comprising a low-pressure tank,

llirst electromagnetic means responsive to the magnitude of the current tlow through the breaker, terminal conductors entering the tank, a high-pressure storage reservoir containing an interrupting. fluid, a circuit-interrupter unit disposed within the tank, a blast Valve for admitting fluid from the reservoir into the interrupter unit, :an iron core mounted around one of the terminal conductors, a coil 'on the iron core, separate electromagnetic means energized by current produced in said coil for opening said blast valve only under heavy fault conditions, and mechanical means responsive to said first electromagnetic means for opening the valve when the current in said coil is below a predetermined amount.

7. In a circuit breaker, in combination, a low-pressure tank, irst electromagnetic means responsive to the magnitude of the cur-rent flow through the breaker, a high-pressure `storage reservoir co-ntaining an interrupting lluid, an interrupting chamber disposed within the tank, contact members separable Within the interrupting chamber, a blast valve for admitting lluid from the reservoir into the chamber, separate electromagnetic means for Vopening the blast valve only under predetermined high -fault current conditions, `and mechanical means oper-able in conjunction with the separation of the contact members for opening the valve in lcase the electromagnetic means does not open the valve prior -to separation of the contact members.

8. A compressed-gas circuit interrupter including contact means separable to establish an arc, contact operating means to effect the opening :and closing motion of said separable contact means, means dening a source of gas under pressure, con-duit means' interconnecting said source with the region adjacent said separable contacts, -a blast valve, blast-valve operating means responsive to the operation of said contact operating means to effect opening of said blast valve and cause a ow of high-pressure gas through said conduit means for arc-extinguishing purposes, and independent electromagnetic means responsive only to predetermined heavy fault current flow through the circuit interrupter to .also effect opening of said blast valve only under predetermined heavy fault current-llow conditions whereby an increased time of valve opening is obtained during fault -current interruption.

9. A compressed-gas circuit breaker including separable contact means separable to establish an arc, a source of high-pressure gas, conduit means for transmitting 4a ow of high-pressure gas from said high-pressure source to said :are to effect the extinction of the same, blast-valve means operable to control said flow of highpressure gas, an operating mechanism actuable to mechanically open the separable cont-act means, a first current-sensing means sensitive to the current magnitude passing through the circuit breaker to actuate the operating mechanism to separate the contacts and open the controlled circuit, connecting means responsive to the opening operation of said mechanism to open the blastvalve means and thereby provide a blast of high-pressure gas to extinguish the established arc, and second current- 'sensing means operable only above :a predetermined current magnitude to open said blast valve independently of the connecting means, whereby an increased time of valve opening is obtained during fault current interruption.

10. The combination of claim 9, wherein the rst and second current-sensing means are current transformers with the primary windings constituted by the terminal `stud of the breaker.

References Cited UNITED STATES PATENTS 2,932,978 4/1960 Newberry 251-130 3,160,726 12/1964 Cromer ZOO-145 FOREIGN PATENTS 894,631 3/ 1944 France. 1,149,772 6/ 1963 Germany.

432,264 4/ 1935 Great Britain.

ROBERT S. MACON, Primary Examiner. 

1. IN A COMPRESSED GAS-TYPE OF CIRCUIT BREAKER, IN COMBINATION, FIRST ELECTROMAGNETIC MEANS RESPONSIVE TO THE MAGNITUDE OF THE CURRENT FLOW THROUGH THE BREAKER, MEANS DEFINING A HIGH-PRESSURE STORAGE RESERVIOR CONTAINING AN INTERRUPTING GAS UNDER PRESSURE, A CIRCUIT-INTERRUPTER UNIT, A BLAST VALVE FOR ADMITTING GAS UNDER PRESSURE FROM THE RESERVOIR INTO THE INTERRUPTER UNIT FOR EXTINGUISHING PURPOSES, MECHANICAL MEANS RESPONSIVE TO SAID FIRST ELECTROMAGNETIC MEANS FOR OPENING THE VALVE AT LOW CURRENTS, AND SECOND ELECTROMAGNETIC MEANS RESPONSIVE TO THE CURRENT FLOWING THROUGH THE CIRCUIT BREAKER FOR OPENING THE VALVE ONLY AT HIGH CURRENTS WHEREBY AN INCREASED TIME OF VALVE OPENING IS OBTAINED DURING HEAVY FAULT CURRENT INTERRUPTION. 